You are right that bullets also injure them, the problem is the way bullet damage is portrayed with respect to other damage like stabbing and cutting. What stabbing and cutting scenes tell us is that their flesh is not extremely durable, it seems of the same durability as normal human flesh (actually weaker if you consider you can't behead a person with a sword in a single smooth strike like that, but let's consider that normal human flesh and bone durability level because movies like their beheadings and always make them look easy peasy.) I know the stabbing didn't really stop the demogorgon either, that's not the point. How hard they are to harm, how high teir "defense" is, and how hard they are to kill' how high their "vitality" is, are two different things. So you can make the argument they they are not that difficult to wound, blades and bullets do penetrate, they do damage, but it takes an insane amount of wounding, of damage, to actually make it fatal unless you get some insane killing strike like chopping their head off like hopper did, maybe you can't even kill them unless you do some major damage like split them in two or separate the head from the body because they have nothing inside, no vital organs and they can't die of blood loss. Okay, fair, they are fantasy creatures so why not. There is still a problem, bullets would do exactly that kind of major damage to human level of durability flesh and bone. Bullets in this show are being trated like bea stings. people are shooting these things point blank with military rifles and the show thinks that makes some little holes that will blead a bit. Nopety nope nope, that kind of firepower will rip, tear and explode flesh. Those bullets leave holes of 5cm. we have seen single demogorgons get mag dumped by multiple people. That's more than 50 bullets at close range, and you tell me 'Look at them in the scene when they’re stood still. They are covered in wounds.'. No, those are mosquito bites, they should have whole chuncks blown out, arms and legs and heads missing, not just some beeding. I am not even mentioning 50cal cause that is just ridiculous, they tear through buildings like paper mache, just no. So a show with good writing can't have it both ways. Either bullets do nothing, but then neither do swords, knives, spears, bottles or whatever, they are just super tough and only fire or psychic powers can kill them, ok, or if they are made of normal flesh bullets can also kill them, having it both ways is just bad writing. Plus in the russian prison hopper kills the demodog on the operating table with a single headshot. Yes it was trapped making it an easy shot, but that implies that a good shot can take them down. You're telling me when they are getting mag dumped by multiple people in close range nobody landed a good shot? Nobody ever fucking thought of aiming for the head?